1. Field of the Invention
This invention relates to an improved marine vessel propulsion and steering system, and more particularly to such a system including a shrouded propeller and tubular forward steering and backing rudders mounted on the aft and forward ends, respectively, of the propeller shroud.
2. Description of the Prior Art
The use of the shrouded propellers on ships and another water craft, including tug boats, barge pushers, and the like as well as pleasure boats (hereinafter, sometimes vessels) to enhance propulsion efficiency, reduce vibration and turbulence in the vessel wake, and to protect the propeller is well known. It is also well known to employ a steering rudder in the form of a short tube mounted for pivotal movement about a vertical axis in position to deflect the propeller race to steer the vessel.
U.S. Pat. No. 2,803,211 discloses a tubular rudder system for a vessel including a forward steering tubular rudder positioned in the propeller race aft of the propeller and a separate backing tubular rudder positioned forward of the propeller and surrounding the propeller shaft. The rudders, which may be substantially identical, are mounted on separate, individually controlled rudder posts for pivotal movement about vertical axes each contained in the vertical plane of the propeller shaft. The propeller is not shrouded, and the rudder diameters are smaller than the diameter of the propeller. There is no suggestion of utilizing both rudders simultaneously for steering both in the forward and backing directions of the propeller. Also, the small diameter and airfoil design of the rudder may restrict water flow and therefore reduce propulsion. The airfoil structure is also expensive to manufacture.
U.S. Pat. No. 3,082,728 discloses a Kort-type rudder using a single tubular member acting both as a rudder and a propeller shroud, with the rudder post being positioned directly above the propeller, and the inside diameter of the rudder tube being great enough to permit the rudder to turn about the rudder post without striking the propeller. The rudder post is mounted to permit tilting of the rudder to assist in banking the vessel.
U.S. Pat. No. 3,115,112 discloses a tubular rudder which may be mounted rearward of the propeller or extending over the propeller as in a Kort design.
While the known tubular rudders, including Kort type rudders in which the rudder tube extends around the propeller, have shown improvement over conventional blade rudders, especially in reducing turbulence in the vessel's wake and the reduction of vibration, these known rudder systems have not proven entirely satisfactory, especially for vessels such as tugs, barge pushers and the like normally having relatively high power and requiring high maneuverability, as well as smaller vessels which frequently operate in crowded waters where maneuverability and reduced turbulence is highly desirable.
It is therefore an object of the present invention to provide an improved propulsion and steering systems for vessels including a shrouded propeller and two tubular rudders disposed one aft and one forward of the propeller.
Another object is to provide such a system which provides increased maneuverability for the vessel.
Another object is to provide such a system is which the two tubular rudders are operable simultaneously to provide greater steering capacity.
A further object is to provide such a system in which the two tubular rudders are mounted on the propeller shroud tube for pivotal movement to steer the vessel.
A further object is to provide such a system in which the tubular rudders are each mounted at its top and bottom to the propeller shroud for increased strength and stability.
Another object is to provide such a system which is both inexpensive to manufacture and easy to maintain.